A microfluidic circuit is described in document WO 2006/018490 in the name of the applicants. The latter is made from a suitable material such as for example PDMS (polydimethylsiloxane) comprising microchannels having typically a width of approximately 100 μm and a depth of approximately 50 μm, wherein can be passed very low flows of a fluid such as air, water, oil, reagents, etc.
A laser beam of which the wavelength is not absorbed by the material comprising the circuit, is focussed on the interface of a first fluid flowing in a microchannel and of a second fluid present at least locally in this microchannel, in order to force or stop the flow of the first fluid in the microchannel, in order to break it up into drops, in order to mix it with the second fluid, etc., the focussing of the laser beam on the interface of the fluids creating a temperature gradient along this interface and provoking a movement of fluids via thermocapillary convection.
As this is known in WO 2007/138178, also in the name of the applicants, this technology was used in order to treat drops in a microfluidic circuit comprising at least one microchannel travelled by the drops. The method used consists in having a laser beam act on the interface of these drops in a carrier fluid or on the interface of the drops in contact, in order to sort drops, form nanodrops from a drop of greater size or to merge drops in contact and provoke reactions between the fluids contained in these drops.